This research is to provide a test procedure for evaluating the performance of agricultural tractor operator roll over protection system (ROPS) that circumvents full scale testing of all systems and tractor combinations. Specific objectives are: 1. To develop a mathematical model that simulates tractor dynamics at the time of impact of the protective frame with the soil. 2. To develop a similitude analysis of the tractor-ROPS and soil interaction during roll over of a tractor to the rear and to the side. 3. To conduct scale model studies and measurements to verify the similitude analysis of the behavior of the tractor-ROPS as it impacts the soil . 4. To conduct a similitude analysis of the performance of a ROPS on an agricultural tractor when subjected to a pendulum impact test. 5. To model the penduulum impact test and verify the similitude analysis by experimental measurements on at least two different sized models. 6. To specify a test procedure for ROPS which incorporates modelling theory and test results to predict the performance of ROPS. Similitude analysis will be completed and physical models will be built and tested to evaluate the suitability of the simulation. Predictive equations will be formulated to generalize the results of the testing program.